Before the invasion of Iraq many commentators wondered what the American exit strategy would be - how would they disentangle themselves from a lengthy commitment to nation-building?

Now the talk is not so much about the end-game - instead US commanders in Iraq are seeking a containment strategy to minimise the threats facing their troops every day.

The casualty toll is mounting - 32 US servicemen have been killed since the start of May. And many more attacks on US forces go unreported.

Nobody expected it would be quite like this, though references to "Vietnam-style quagmires" are premature

The Pentagon's insistence that it is not facing a guerrilla war seems to be undermined by the facts on the ground with clear suggestions that there is more co-ordination behind the attacks than defence department chiefs would like to admit.

Procedures and routines need to be constantly monitored to reduce the vulnerability of small units on the ground.

US troops are also going onto the offensive seeking to pre-empt attacks before they happen; though everything here depends upon the quality of the intelligence that is available.

And here is the problem. The more the Americans can establish normal life in Iraq so the more likely they are to reap the benefits in terms of intelligence.

The more the Saddam Hussein loyalists can disrupt that sense of normality the more unwilling people will be to co-operate with the Americans.

Nobody expected it would be quite like this, though references to "Vietnam-style quagmires" are premature.

Leaders escaped

The picture on the ground in Iraq is mixed. Significant parts of the country are relatively quiet.

The war did not end as the Americans had planned

But there are serious and mounting difficulties in Baghdad itself and along the main routes leading north, west and east from the capital.

A major US security operation has already been underway for some days on Highway One leading north towards the former-regime's ideological home in Tikrit.

What is equally clear is that the war did not end as the Americans had planned.

There was no massive sweep southwards towards Baghdad from the Turkish border and many of the regime's supporters, including its top leadership, have somehow escaped and blended into the countryside.

'Untidy and dangerous'

Troop numbers may not be a critical issue right now. US commanders say they can cope with the 150,000 or so soldiers currently on the ground, to be bolstered by some 30,000 more foreign troops by the autumn.

But some military experts wonder if they might have needed many more troops in the immediate aftermath of the fighting.

US Defence Secretary Donald Rumsfeld has hinted that more US troops could be on offer if required. But this burden cannot be sustained for years.

And a failure to formally internationalise the force by bringing it into the United Nations' orbit is clearly adding to the reluctance of some potential contributors like France and India.

The US experience in Iraq so far is not a triumph, but it is probably not an unmitigated disaster either, (not yet anyway).

True there have been some errors and false starts - especially on the political front.

But nation-building takes time. It requires the maintenance of security, the restoration of basic services and the creation of institutions.

It is an untidy and often dangerous business. And there is probably no alternative for the Pentagon beyond seeking to share out the burden as best it can.